N-isopropylacrylamide (NIPAM) and acrylic acid (AA) copolymer microspheres with various compositions were prepared by a reverse suspension polymerization technique. The microspheres thus prepared were employed as micro-reactors for the synthesis of Fe₃O₄ and the deposition of SiO₂ in situ. In this way, several kinds of SiO₂-Fe₃O₄-P(NIPAM-co-AA) magnetic composite microspheres with different surface morphologies were prepared. It was demonstrated that the surface structures of the composite microspheres could be tailored to a certain extent by varying the ratio of the two monomer units in the template (microgels), the amount of Fe₃O₄ adsorbed and the amount of SiO₂ deposited. The magnetic composite microsphere surface was modified by the NH₂ groups via silanization reagent (3-aminopropyltrimethoxysi- lane). It might be expected that this functional material can be applied for recognition of biomacromolecules and in biological medical fields.

Key words: reverse suspension polymerization, microgel template, magnetic composite microsphere, shift of magnetic hysteresis loop